GHCi does not support some TH elements, while those elemenst are working in hs files
Hello. Below is a code, which works when using runhaskell, but does not work in GHCi.
In GHCi we get following error: runQ [d| instance ( y ~ (t->t) ) => Member Vector y where member v = test |] <interactive>:19:6:
Exotic predicate type not (yet) handled by Template Haskell
y ~ (t -> t)
code:
{-# LANGUAGE TypeFamilies #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE UndecidableInstances #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE TemplateHaskell #-} module Main where
import Language.Haskell.TH
class a ~ b => HEq a b
test :: a -> a test x = x
data Vector class Member a b where member :: a -> b
main :: IO () main = print =<< runQ [d| instance y ~ (t->t) => Member Vector y where member v = test |]
Trac metadata
Trac field | Value |
---|---|
Version | 7.7 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | GHCi |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | hvr |
Operating system | |
Architecture |